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 DENSO's diesel after-treatment system has a diesel particulate filter (DPF) that traps particulate matter (PM) contained in a diesel vehicle's exhaust gas. When the amount of trapped PM reaches a predetermined level, the system raises the temperature of the DPF, which causes the catalyst-carried thereon to burn the PM and regeneration the DPF. The diesel after-treatment system consists of: a DPF; a DPF pressure sensor for measuring the pressure difference of the exhaust gas before and after passing through the DPF; exhaust gas temperature sensors mounted in front of and behind the DPF, and an engine control unit (ECU) that uses information from the sensors to estimate and calculate the amount of trapped PM. When the amount of PM reaches a specific level, unburned fuel and exhaust gas are supplied to the DPF in a post-injection (a fuel injection that occurs in a single combustion after the main injection to supply the DPF with unburned hydrocarbon and exhaust gas without burning fuel in the cylinder). The unburned fuel and exhaust gas react with the catalyst-carried thereon, and raise the temperature high enough (over 600℃) to burn the PM. However, the temperature is raised too high, the catalyst will deteriorate. Therefore, DENSO's diesel after-treatment system adjusts the post-injection quantity to keep the DPF temperature within an appropriate range.
Diesel Particulate Filter (DPF) DENSO's cylindrical DPF includes a monolithic carrier whose cells are alternately plugged on each end. Each cell wall has an infinite number of very fine pores of high porosity, which heightens filtration efficiency to more than 90 percent while reducing gas-flow resistance so it does not affect engine performance. The trapped PM is then burned through a catalytic reaction. DENSO's DPF, which is made of cordierite ceramic, costs less in
materials and is easy to produce, making it a less-expensive option. As the amount of the PM trapped by the DPF increases, the pressure of the exhaust gas before and after passing through the DPF increases. This is how the system estimates the accumulated amount of PM. Since the pressure difference is influenced by the volume of exhaust gas, the temperature of exhaust gas passing through the DPF and the airflow are also referred to when estimating the accumulated amount of PM. DENSO's DPF pressure sensor for exhaust gas is designed to protect the sensor elements from exhaust gas, thereby achieving high accuracy and reliability. Exhaust Gas Temperature Sensor One of the main features of this exhaust gas temperature sensor is the fine diameter of the temperature sensor portion, which provides highly accurate information. [Contact] |
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